Torsional vibration damper

Abstract

Torsional vibration damper which is suitable for dampening the motion of a rotatable element, said torsional vibration damper comprising an ‘actuation’ element which is connectable to the rotatable element, an ‘inertia’ element arranged co-axially and rotatably with said actuation element, an enclosed volume between said inertia element and said actuation element where a cross section through said enclosed volume taken on a plane which is parallel to the axis of the actuation element comprises at least one ‘axial’ portion which is arranged essentially parallel to the axis of the actuation element, an Electro-Rheological or a Magneto-Rheological fluid arranged at least in a part of said enclosed volume, and an electric or a magnetic field generator in the form of a coil which generates an electric or a magnetic field which passes through at least a portion of said enclosed volume. The field generator is integrated into the torsional vibration damper in such a way that a majority of the magnetic or electric field lines generated by the field generator pass through said ‘axial’ portion of said enclosed volume. In this way, an effective torsional vibration damper is provided.

1 . Torsional vibration damper which is suitable for dampening the motion of a rotatable element, said torsional vibration damper comprising:
 an “actuation” element which is connectable to the rotatable element,   an “inertia” element arranged co-axially with said actuation element and arranged rotatably with said actuation element,   an enclosed volume between said inertia element and said actuation element where a cross section through said enclosed volume taken on a plane which is parallel to the axis of the actuation element comprises at least one “axial” portion which is arranged essentially parallel to the axis of the actuation element,   an Electro-Rheological or a Magneto-Rheological fluid arranged at least in a part of said enclosed volume, and   an electric or a magnetic field generator in the form of an electric field generator or a coil respectively which generates an electric or a magnetic field respectively which passes through at least a portion of said enclosed volume,   
     wherein:
 the field generator is stationary with respect to the inertia element and the actuation element; 
 the torsional vibration damper further comprises an insulating element made from a material with a low magnetic permeability or with a low electric conductivity arranged adjacent to the field generator, such that the magnetic or electric field lines pass around said insulating element; and 
 said field generator is integrated into the torsional vibration damper in such a way that a majority of the magnetic or electric field lines generated by the field generator pass through said “axial” portion of said enclosed volume. 
 
   
   
       2 . Torsional vibration damper according to  claim 1 , characterized in that said magnetic or electric field lines pass essentially perpendicularly through said axial portion of said enclosed volume. 
   
   
       3 .- 4 . (canceled) 
   
   
       5 . Torsional vibration damper according to  claim 1 , wherein said field generator is arranged in a housing which is arranged co-axially with the actuation element. 
   
   
       6 . Torsional vibration damper according to  claim 5 , wherein there is a bearing between the housing and the actuation element. 
   
   
       7 .- 8 . (canceled) 
   
   
       9 . Torsional vibration damper according to  claim 1 , wherein the torsional vibration damper further comprises seals which prevent the ER or the MR fluid arranged in the enclosed volume from contacting the bearings. 
   
   
       10 . Torsional vibration damper according to  claim 1 , wherein the enclosed volume is filled with an amount of ER or MR fluid such that during operation, essentially only the “axial” portion of the enclosed volume is filled with fluid. 
   
   
       11 . Torsional vibration damper according to  claim 1 , wherein the enclosed volume is at least partly filled with an ER or an MR fluid having a concentration of particles lower than normal ER or MR fluids.